tar -pczf rchive.tar.gz /home/USERNAME

You can read more about tar by reading it’s manual.

man tar

Happy reading !

If you have any questions don’t hesitate to leave a comment.

dd if=/dev/sdX of=MBR.bck bs=512 count=1

Please note that you have to replace /dev/sdX with your actual drive. This can be /dev/sda, /dev/hda, etc.

How to restore de MBR record

dd if=MBR.bck of=/dev/sdX bs=512 count=1

Again you have to replace /dev/sdX with your actual drive.

If you also want to keep a human readable copy of the partition table you can run:

fdisk -l > part.table

I hope it helps !

First of all I will start by telling you what you can do using the “screen” command.
Many times as a linux sysadmin you will need to run multiple commands at once. You are probably doing this by opening multiple ssh sessions but there is a better way to do it !
Also as a sysadmin you probably had to run a command or script that is taking hours to finish like a rsync. This usually requires you to keep the ssh session open as if you close it the command or script will also be closed.

If you ever faced any of those problems then it’s probably time to learn about the screen command.

Screen – makes it possible to run multiple full-screen pseudo-terminals from one real terminal, and lets you manipulate and save your screen input and output, copy and paste between windows.

In this tutorial I will only present how you can run a command that is taking hours to complete in a screen.

First of all make sure that you have screen installed. If you don’t you can install it using yum, apt-get or any other package manager that you might have on your server.

yum install screen

Now type in:

screen

This will start a new screen for you. You could also name you screen using the -S option. Something like:

screen -S 1

In this case I named the screen “1″.

The screeen will look like any other ssh window.
You can now type in your command that you want to run.

If you want to detach from the screen and still keep the command running you can do this by pressing:

Ctrl-a d (that is press Ctrl-a, release and press d)

If you want to reatach to a screen you simply type in:

screen -r

Other options that you have when you are in a screen are:

1. To create a new screen:

Ctrl-a c

2. To switch between screens:

Ctrl-a n

3. And many others.

For more help on this you can use:

man screen

Hope it helps!
If you have any questions just leave a comment.

The command works by setting the immutable bit of the file.

How you can make a file immutable ?
Note: This command must be run as root

chattr +i file_name

An example use would be:

chattr +i ftp.log

Now if I want to delete the file I would get:

rm -f ftp.log
rm: cannot remove `ftp.log’: Operation not permitted

Please remember that this was done as root !

If you want to unset the immutable bit you can use the command:

chattr -i file_name

If you want to check what are the attributes of a file you can do so using the command lsattr:

lsattr file_name

In our example we would be getting:

lsattr ftp.log
—-i——– ftp.log

Please notice the immutable bit !

Hope it helps!
If you have any questions just leave me a comment.

find where-to-look criteria what-to-do

All arguments to find are optional, and there are defaults for all parts.  (This may depend on which version of find is used.  Here we discuss the freely available GNU version of find, which is the version available on YborStudent.)  For example where-to-look defaults to . (that is, the current working directory), criteria defaults to none (that is, show all files), and what-to-do (known as the find action) defaults to -print (that is, display found files to standard output).

For example:

find

will display all files in the current directory and all subdirectories.  The commands

find . -print
find .

do the exact same thing.  Here’s an example find command using a search criteria and the default action:

find / -name foo

will search the whole system for any files named foo and display them.  Here we are using the criteria -name with the argument foo to tell find to perform a name search for the filename foo. The output might look like this:

/home/wpollock/foo
/home/ua02/foo
/tmp/foo

If find doesn’t locate any matching files, it produces no output.

The above example said to search the whole system, by specifying the root directory (/) to search.  If you don’t run this command as root, find will display a error message for each directory on which you don’t have read permission.  This can be a lot of messages, and the matching files that are found may scroll right off your screen.  A good way to deal with this problem is to redirect the error messages so you don’t have to see them at all:

find / -name foo 2>/dev/null

Note:Article based on: http://www.hccfl.edu/pollock/Unix/FindCmd.htm

 strace -p PID

Where PID is the process ID. Whis will show you what that process is doing in real time.

This is usefull for detecting  exploits or the source of a hang process.

To detach from that process simply press CTRL + C.

Hope it helps ! Leave a comment if you have any questions.

1. Login to your server as root
2. Run the fallowing command

chmod 0700 /usr/bin/wget

Please note that disabling wget might cause some scripts to stop working. A known problem is that Fantastico will stop updating after this. The solution is pretty easy…
Before you disable wget make sure that you do a copy of it with the initial permissions. You can use any name that you want, the fallowing is just an example:

cp /usr/bin/wget /usr/bin/wget_secret

In the Fantastico configuration input the location to wget as:

/usr/bin/wget_secret

If for some reason you you want to revert the change you simply have to do:

chmod 0711 /usr/bin/wget

If you have any questions or suggestions please leave a comment.

Importing a mysql database

1. Login to your server as root or as a user that has access to that database
2. Type the fallowing command

mysql -uUSERNAME -pPASSWORD database_name < database.sql

Exporting a database

1. Login to your server as root or as a user that has access to that database
2. Type the fallowing command

mysqldump -uUSERNAME -pPASSWORD database_name > database.sql

Notes:

USERNAME and PASSWORD is a combination that has access to that database. It can actually be the mysql root user.
database.sql is the file imported or the file to which you do the export.

Hope this helps !

Simply run as root:

mii-tool

This will output something like:

eth0: negotiated 100baseTx-FD, link ok